<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script>

        foo1();

        function foo1() {
            let x = 1;
            let y = 2;

            foo2(x, y)

            x++;
            y++;

            console.log('x, y', x, y);

        }


        function foo2(a, b) {
            foo3(a, b);

            a++;
            b++;

            console.log('a, b', a, b);
        }

        function foo3(i, j) {
            console.log('i, j', i, j);

        }






    </script>
</body>

</html>